Bookmarked sites keeping in Firefox cache (on your hard drive)only if you visit the site that the page may load quicker the next time you visit it. write in address bar '''about:cache''' and you see the restored cache: Memory cache device, Disk cache device and Offline cache device, click the '''List cache entries''' to see the entries. see also: [http://support.mozilla.org/en-US/kb/How%20to%20clear%20the%20cache How to clear the cache] ------------------------------------------------------------------------------------------ see also: [http://kb.mozillazine.org/Plugin-container_and_out-of-process_plugins Plugin-container] ------------------------------------------------------------------------------------------ see also how to prevent or work around high CPU usage in Firefox : [http://kb.mozillazine.org/Firefox_CPU_usage Firefox CPU usage] thank you Please mark "Solved" the answer that really solve the problem, to help others with a similar problem.